Drafting instrument



April 1963 G. s. DOLGORYUKOV 3,375,589

DRAFTING INSTRUMENT Filed Dec. 19, 1963 v 2 SheetsSheet 1 IN VENTOR.

gm sbo go'lukq/ April 2, 1968 G. s. DOLGORUKOV 3,375,589

DRAFTING INSTRUMENT Filed Dec. 19, 1963 2 Sheets-Sheet 51 //////////%g!m w United States Patent Ofifice Patented Apr. 2., 1968 3,375,589DRAFTING INSTRUMENT Gregory S. Dolgorukov, Ferndale, Mich. (407 FisherBldg, Detroit, Mich. 48202) Continuation-impart of abandoned applicationSer. No. 835,118, Aug. 20, 1959. This application Dec. 19, 1963, Ser.No. 331,800

3 Claims. (Cl. 33104) ABSTRACT OF THE DISCLOSURE The present applicationdiscloses a drafting triangle which provides for using the sides formedat the inner opening of the triangle for drawing lines at anglesdifferent than those which can be drawn parallel to the outer guidingsides of the triangle, and particularly drawing with the use of a 45 90triangle lines at and 60 angles. The inner sides parallel to the outerguiding sides are not intended to be used as guiding means and haveprovided therein finger lift recesses of arcuate cross section formingtwo sharp edges at the intersection of said recesses with the top andbottom surfaces of the triangle body and therefore disposed at thehighest possible distance from the drawing with the triangle of a giventhickness.

This invention relates to drafting instruments and more particularly butnot exclusively to improved drafting triangles.

The present application is a continuation-in-part of my copendingapplication Ser. No. 835,118, filed Aug. 20, 1959, for DraftingInstruments, now abandoned.

One of the difficulties in the use of drafting triangles results fromthe necessity of picking up the triangle for the purpose of moving it onthe drawing, such as removing it from the ink line and/ or turning itover. The thickness of a drafting triangle being usually from to doesnot provide a convenient finger hold thereon, and therefore ink linesare often smeared and considerable inconvenience to the user isotherwise caused in attempts to raise the triangle from the drawing.

It has been attempted to solve this problem by providing so-calledfinger lifts or beveling notches of the segmental shape with three ofsuch notches usually provided k on one surface of the triangle body andtwo or three on the other. It has been found, however, that such fingerlifts are not fully operative for the intended purposes since theyrecess the body thickness only through very short distance and at theirmiddle portions at that. The user would actually have to have a longnail on his thumb with which to get under the triangle at such shortthumb recesses, which is not fully practicable.

It has been attempted to solve this problem by providing so-calledcontinuous finger lifts, or, in effect, beveling L the inner sides ofthe triangle from both top and bottom surfaces thereof to provide avirtually sharp edge. It has been found, however, that while suchexpedient operates satisfactorily while the triangle is new, as timegoes on and the beveling becomes smooth, such expedient actuallyproperties of the material used rather than to the construcsofter vinylplastics did not solve the difiiculty of nicking, sincethe edges of suchtriangles, while not brittle, are so soft that they can be easily nickedwith ones nail; since their weak corners easily bend in fall, precisionof such triangles is easily destroyed. In their prolonged use themiddles of the guiding sides wear and cause formation of valleystherein.

In the search for greater transparency of such triangles and in themistaken belief that highly polished surfaces are necessary therefor,resulting use of highly polished plastic sheeting made draftingtriangles, by reflecting the windows and the overhead lights directlyinto draftsmens eyes, a source of eye strain cumulating through a periodof years in injurious effect on draftsmens eyesight.

One of the objects of the present invention is to provide an improveddrafting instrument such as drafting triangle whereby the abovedifiiculties and disadvantages are overcome and largely eliminatedwithout introducing other problems or appreciably increasing the costsinvolved. Another object of the invention is to provide an improveddrafting triangle which is more convenient to use and particularly ismuch easier to pick up from the drawin g, and therefore is moreefiicient in use. v

A further object of the present invention is to provide an improveddrafting triangle which can be used for inking with the possibility ofsmearing wet inked lines be ing greatly reduced. I A still furtherobject of the present invention is to provide a drafting triangle madeof harder plastics and therefore presenting a harder edge but with thetendency of such edges and corners to nick, chip and break off, asobserved in conventional triangles, being greatly reduced.

A still further object of the present invention is to provide animproved drafting triangle of the nature specified in the precedingparagraph in which nicking of the edges both caused by hitting hardobjects as well as by formation of cracks, due to internal stresses ormachining, is greatly reduced.

A still further object of the present invention is to provide animproved 9045 triangle including means provided therein for drawing 30degree and degree lines inclined in either direction.

A still further object of the present invention is to provide animproved triangle,-the use of which greatly reduced general fatigue andeye strain. 1

Further objects and advantages of this inventionwill be apparent fromthe following description and appended claims, references being had tothe accompanying drawings forming a part of this specification, whereinlike reference characters designate corresponding parts in the severalviews.

FIG. 1 is an elevational view showing an improved 45 ".-45 triangleembodying the-present invention.

FIG. 2 is a fragmentary sectional view taken in the direction of thearrows on the plane passing through the section line 22 of FIG. 1.

FIG. 3 is a fragmentary sectional view taken ,at'the direction of thearrows on the section plane passing through-the line 33 of FIG. '1.

FIG. 4 is an elevational view showinga 30-90-60 drafting triangleembodying the present-invention.

FIG. 5 is a fragmentary view showing on an enlarged scale the portion ofthe triangle of FIG. 4 encircled by the circle 5.

FIG. 6 is a fragmentary sectional'view taken in the direction of thearrows on the section plane passed through the section line '66 of FIG.4.

FIG. 7 is a view showing on an enlarged'scale the corners of thetriangle of FIG. 4, encircled in FIG. 4 by the circles 7.

FIG. 8 shows an improved 45 -90-,45 triangle with provision therein todraw lines at 30 and 60 to the lines drawn along its guiding sides.

FIG. 9 is a diagrammatic view giving outline of the center aperture ofthe triangle of FIG. 8 and illustrating the angles formed by the innerguiding sides thereof.

FIG. 10 is a perspective view of one of the triangle corners constructedin accordance with the present 1nvention.

FIG. 11 is a fragmentary view showing the triangle of FIG. 8 providedwith finger lifts such as disclosed herein and illustrated in FIG. 2.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways within the scope of the claims. Also, it is to be understood thatthe phraseology and terminology employed herein is for the purpose ofdescription and not of limitation.

In the drawings there are shown, by way of example, drafting trianglesembodying the present invention. It is to be understood that the novelfeatures of the constructions illustrated therein are representedgraphically in a greatly exaggerated manner in order to permit makinggeometric constructions illustrating such features. Showing thesefeatures of construction to exact proportional scale would make thedrawings impracticably large or the novel features of construction sosmall as not to be legible.

Referring specifically to FIGS. 1-3, the drafting triangle illustratedtherein comprises a fiat body generally designated by the numeral 11 andhaving top and bottom surfaces and outer guiding sides 12, 13, and 14.The sides 12 and 13 form between them an angle of 90, and the third sideor hypotenuse 14 makes the angles of 45 with said sides 12 and 13,respectively. The guide sides are of a square cross section, as is bestshown in FIG. 2, and are adapted to guide an instrument point, such asthat of a pencil or an inking pen.

In the middle portion of the body 11 there is provided a triangularaperture having inner sides 15, .16, and 17, generally parallei to theouter guiding sides of the triangle body. The inner sides 15, 16, and 17are not guiding sides, but are provided with concave recesses 20, v21,and 22, respectively, to impart to the inner sides a concave crosssection such as illustrated in FIG. 2. The recesses are symmetrical withrespect to the axis of the cross section in order to providesubstantially sharp edges, such as edges 22a and 22]), substantiallyalong the entire lengths of therespective inner sides and both along thetop and bottom surfaces of the body. By virtue of such a constructionthe sharp edges provide a more effective hold for the users thumb, withsuch sharp edge being disposed twice as high from the drawing surfacethan is the case with beveling the inner sides from the top and bottom.Wearing out of the triangle affects such edges very little and thereforetheir effectiveness is preserved for many years.

In accordance with the invention, means are provided eliminating thepossibility of origination of cracks and breakage of the triangle at thecorners of the inner aperture. It has been found that drafting trianglesusually break through their corners even if such corners have squarecross sections. Presence of sharp edges such as 22a and 22b in thecorner would promote such breakage and could, in effect, defeatadvantages of the present invention.

In accordance with the present invention, the corners of the apertureare rounded as illustrated in the drawings. The rounded corners such asillustrated in the drawings may be formed by drilling them with ball orspherical mills with which the recesses are cut. By virtue of such amethod, rounding of the cornersand provision of recesses may be made ina single operation, such as by recessing the inner sides with aspherical milling cutter the elevation of which with respect to work isadjusted to have its center on the axis of the body thickness, andthereupon sinking and withdrawing such cutter at each corner.

Of course, these two operations maybe performed in reversed order. Also,the corner holes may be drilled and relieved or chamfered at the edgesin separate operations first, and thereupon the aperture may be cut outwith square sides and recessed as explained above to provide thecontinuous concave finger lifts as explained. It is of importance thatthe sharp edges of the corners are relieved for a small distance, suchas .010 as indicated at 25 in FIG. 3. By virtue of such'an expedient,breakage of the triangles at the corners are greatly reduced as comparedwith conventional triangles.

FIG. 4 shows a 3090-60 triangle in which the continuous finger lifts areformed by cutting them in the inner sides of the triangle body at theaperture to extend further into the sides than do the corners of theaperture as illustrated in FIGS. 4 and 3 wherein such recesses aredesignated by the numerals 30, 31,.and 32. In this construction thesharp edges of the body at the round corners of the aperture are alsoremoved, as is best illustrated in FIGS. 5 and 6 wherein such relief onthe corners is designated by the numerals 33 and 34. Since these cornersare not guiding elements the precise depthof the relief is not criticaland may be made larger.

The triangle illustrated in FIGS. 1-3 as well as other trianglesillustrated and described below are made of hard plastic to provide hardedges and particularly from cast and annealed acrylic sheets, from whichsuch triangles are cut by milling operations. While such materialprovides for hard guiding sides not susceptible of nicking by nailpressure and rapid wear, causing bowing or caving in wear of the sidesby the action the instrument points, the brittleness of such materialmakes their sharp edgessusceptible to deterioration because of theformation of minute cracks at sharp edges in the process of milling.Such cracks rapidly grow inwardly of the body of the triangle andcausing crumbling out of the material when two adjacent cracks meet. Inaddition, such edges are exceedingly susceptible of nicking even bylight impacts on hard objects, such as frames of the drawing boardsshould the triangle happen to fall down. It is well. appreciated in theart that even a small nick on a triangle guiding side may cause thedraftsman to discard the triangle as being a source of faulty work andextreme annoyance.

The sharp edges of the guiding sides along the top and bottom surfacesof the body 11 are cut away as indicated at 18 and 19 in FIG. 2. It ispreferred to cut such edges to a uniform depth around the entiretriangle for the depth of from .003" to .010", preferably at a 45 angle,thus making the exposed edges of the guiding sides forming the angles of135 instead of The edges so produced may be polished, if desired. Itshould be undertood that. the depth of such edge relief on guidingsidesis critical:

and it should not affect squareness of the sides. Generally this relief,in spite of its critically important efiect, isso small as to beinvisible by the naked eye and its presence may not be realized by thetriangle user.

By virtue of the above described expedientthe sharp edge in which minutecracks have been formedin milling are removed, and a single 90* edge issubstituted by two edges, producing a hard andstrong edge thathasextremely long life, makes smearing of ink lines less likely, andprovides formore pleasant handling of the triangle. This expedient has anumber of further important advantages.

FIG. 8 illustrates at 45-90-45 triangle having outer.

guiding sides 40, 41, and 42 and a central aperture hav-.

ing inner guiding sides 43,44, 45, '46, and 47. It isimportant toappreciate that in this particular triangle all five inner sides of thebody at the inner aperture are guiding sides, i.e., are adapted toguide. instrument points. It is also important to appreciate that whilein the triangles of FIGS. 1 and 4 the sides of the inner opening aregenerally parallel to their respective outer guiding sides, in thoseconstructions this relationship is not of a precision nature and suchparallelism is sufficient if it satisfies the requirements ofappearance. On the other hand in the triangle FIG. 8, the angularrelationship of the inner sides with respects to the outer sides is aprecision relationship. Particularly, the inner side 43 is parallel tothe outer guiding side 40 and perpendicular to the outer guiding side41. The inner guiding side 44 is parallel to the outer guiding side 41and is perpendicular to the outer guiding side 40. The inner guidingside 46 is parallel to the outer guiding side 42 and forms angles of 45with sides 40 and 41. The inner side 47 forms an angle of 60 with theouter guiding sides 41, and a 30 angle with the outer guiding side 40.Also, the sides 45 and 47 make the angles of 105 and 75 with the sides42 as illustrated. In addition, the guiding sides of the aperture makebetween themselves angles of 90, 120, and 105 as illustrated in FIG. 9.Thus, the angles most useable in an engineering drawing maybe laid offwith the use of the triangle of FIG. 8 without changing to a 30-90-60triangle or to a protractor. The inner angles of the aperture may berounded on a radius such as in order to produce a more durable triangleand to enable drawing rounded corners and fillets without the use of acompass.

An important advantage of all of the triangles illustrated herein liesin the provision of outer corners which resist chipping and breaking, anexceedingly objectionable occurrence frequently observed in conventionaltriangles.

It is important to appreciate that mere rounding such corners is notfully effective to eliminate such condition, and this fact proved verymisleading to those skilled in the art. I have found that this resultsfrom the fact that triangles seldom fall remaining in a positionperpendicular to the floor. In a fall, a triangle usually assumes aninclined position and hits the floor not with the rounded but with thesharp edge of the corner which sharp edge mere rounding of the cornersdoes not eliminate. As a result of such fall, a large scale or piece ofthe plastic is broken ofif the corner, and the final result is usuallythe same as that which follows if a triangle hits the floor with a sharpor unrounded corner.

In accordance with the present invention the sharp edges at the roundedtriangle corners are removed both at the top and bottom surfaces of thetriangle as is best illustrated in FIG. 10, wherein the sharp corner 50at which the two guiding sides meet is eliminated to provide a roundedsurface 51. The sharp edges 52 and 53 formed by such rounding at the topand bottom surfaces of the triangle body are eliminated by angular cutsto provide surfaces such as illustrated at 54. Use of the designatingnumeral for a similar surface at the bottom of the triangle is avoidedin FIG. to prevent confusion of the leader lines.

In accordance with the invention the radius on which rounding of thecorners of the triangles are made is inversely proportional to the sizeof the angle, i.e., the larger is the angle the smaller is the radius onwhich such rounding is made. Since provision of the surface such as 54depends in its size on the radius at which the corners are rounded, thesame relationship remains with respect to provision of such surface. Iprefer to provide such surfaces to approximately one-half of such circleas is best illustrated in FIG. 7, at an angle from to 50. Use of thestraight cut is preferable as easily done, but use of curved cuts may bestill more advantageous.

As illustrated in said FIG. 7, triangle shown therein has the largestradius at its corner, while the 90 corner has the smallest. Under someconditions, and particularly with smaller triangles, rounding of the 90corner may be eliminated entirely. The size of the corner radii alsodepends on the size of the triangle. With the large triangle, such asthose of 24" size, such radii are much greater than in the correspondingcorners of small triangles. For instance, a 30 corner of a 24" trianglemay have a radius of while the same corner of an 8" triangle may havethat radius equal to only ,6

Within the last 20 years or so the eye strain in drafting work increasedat an alarming rate, producing severe headaches and nervous strain andcausing inability of a draftsman to continue with drafting work andretirement several years earlier than before. Such condition prevailedin spite of the fact of presumably better lighting in drafting rooms.

I have found that while the intensity of illumination did increase ingeneral and in drafting rooms in particular, the lighting fixturesbecame very large, often being continuous from wall to wall of adrafting room and having considerable width. In addition, the windows indrafting rooms have also greatly increased in size. This made itimpossible to eliminate reflection of such lighting fixtures, shiningdirectly into draftsmens eyes from the reflecting surface of a draftingtriangle, merely by slightly changing the working position as waspossible to do with smaller round lights before the advent of thepresent-day fluorescent lighting fixtures.

Another difiiculty resulting from such a condition is found in thenecessity of straining draftsmens vision to distinguish a transparentedge of the drafting triangle, particularly those made of colorlessacrylic plastic from the lines on the drawings, particularly inoperations such as section lining, in the performance of which thedraftsman has to set an almost invisible edge of a drafting trianglefrom the thinnest line on the drawing. While old celluloid material hadamber tint which became darker with age, acrylic plastic, a material ofthe highest transparency, remains colorless, greatly enhancing the eyestrain problem. Attempts have been made to use colo acrylic such asgreen or pink fluorescent, providing a clearly visible anddistinguishable edge on the triangle. It has been observed, however,that such expedient was not only ineffective to relieve the eye strainbut in many cases increased it. I have found that this conditionresulted from providing a color contrast between the triangle body andthe paper, which is also an injurious condition. Some draftsmen havingparticularly sensitive eyes see a complementary color on the paper whenusing such color triangles.

In accordance with the present invention, the top surface of thedrafting instruments such as triangles is made non-reflecting, such asproviding a satin or frosted finish thereon. By virtue of such anexpedient, reflections of overhead lights and windows are eliminated,thus relieving severe eye strain on draftsmens eyes.

It should be understood in providing the satin or frosted finish, thatin cases of 4590 45 triangles such as shown in FIGS. 1 and 8, it isgenerally suflicient to provide such finish on one surface only and usethe triangle to have its frosted or satin finish surface as the topsurface. Such triangles need not be turned over to get all of the angleswhich may be set with such a triangle. On the other hand with 30-90-60triangles, such as one shown in FIG. 4, it is necessary to provide thefrosted or satin finish on both top and bottom surfaces thereof since itis necessary in use to turn such triangle over.

In addition, in acordance with the invention I eliminate use of thecolors in a manner used before and use acrylic material of very lightgreen or yellow color, in effect only faint light color tint, sufiicientonly to distinguish the edge of the triangle but not sufiicient to givethe color contrast of the objectionable nature. Triangles made ofacrylic material of a very light green tint proved to be of greaterbenefit to draftsmens eyesight and their working efficiency.

It will be understood that the guiding edges of all trianglesillustrated herein are constructed as illustrated in FIG. 2 to eliminatethe sharp edges and that all of the corners of the triangles may beconstructed as illustrated in FIG. 7.

By virtue of the above described constructions the objects of thepresent invention listed above and numerous additional advantages areattained.

I claim:

1. A drafting triangle comprising a body made oftransparent sheetmaterial and having top and bottom surfaces, with each of said surfacesadapted to lie on straight surface in full surface-to-surface contacttherewith, two outer guiding sides forrning between them an angle of 90degrees, with the third outer guiding side forming 45 degree angles withsaid two sides, respectively, a single central aperture provided in saidbody to form five inner point-guiding squared sides, with the three ofsaid inner sides being parallel to the outer guiding sides,respectively, and with the remaining two of said inner sides forming 30degree and 60 degree angles with each of said two sides, respectively,in either direction, with each of the two inner guiding sides formingthe 90 angle therebetween being decreased in their respective lengths bythe provision of said two remaining sides by a length smaller than onehalf of the total length of each said guiding side forming the 90 angletherebetween.

2. The drafting triangle defined in claim 1, with at least 45 degreecorners formed by the outer guiding sides being rounded and relieved toremove their sharp edges at both top and bottom surfaces of the body,and all guiding sides being square and angularly chamfered forapproximately .003" to .007" to remove the sharp line edges thereof atboth top and bottom surfaces of the triangle.

3. The drafting triangle defined in claim 2 with the sides of thetriangle at the central aperture thereof which are parallel to the outerguiding sides of said triangle being provided with finger lift recessesof arcuate concaved cross section symmetrical with respect to thethickness of the triangle body to form sharp edges along the inner sidesof the central aperture extending inwardly thereof, with the radius ofcurvature of said recesses being larger than half of the thickness ofthe triangle body.

References Cited UNITED STATES PATENTS 583,058 5/1897 King 33--112509,3-35 11/1893 Stowell 33--107. 1,334,145 3/1920 Eaton 33107 X2,181,081 11/1939 GanaWay 3352 X 2,401,265 5/1946 Nash 33104 2,428,69910/1947 Elbert et al 33-110 2,512,852 6 1950 Dolgorukov 33.174 l2,589,525 3/1952 Absher 33-104 2,610,407 9/ 1952 McQuaid 33-1042,748,474 6/1956 Brown 33--18 X 2,820,294 1/1958 Dolgorukov 33-104 13,103,071 9/1963 Dolgorukov 33-112 FOREIGN PATENTS 572,288 2/ 1964France.

919,388 11/ 1946 France.

606,280 11/ 1934 Germany.

709,790 8/1941 Germany.

139,110 2/ 1920 Great Britain.

581,013 9/1946 Great Britain.

520,237 3/ 1955 Italy.

124,367 2/ 1928 Switzerland.

OTHER REFERENCES Publication: Designers Triangle, copywright 1947, byDolgorukov Mfg. Co. (Copy Group 430.)

HARRY N. HAROIAN, PrimaryExaminer.

